The present invention relates to an apparatus for opening and closing an open end face of a core tube utilized at a time when a fork is charged or uncharged, that is, when a fork is inserted or not inserted in the core tube.
In general, it is necessary for a core tube to close the open end face thereof with a fork being charged thereinto in a case, for example, where a semiconductor wafer oxidation diffusion process is carried out in the core tube and, accordingly, in a known art, there is provided a core tube opening and closing apparatus capable of opening or closing the open end face of the core tube in the two modes of when a fork is charged and when a fork is not charged.
One typical example of a conventional core tube opening and closing apparatus disposed in front of the core tube includes two lid members made of silica plates in shape of discs utilized at times when a fork is charged and not charged.
One of the lid members utilized at the time when the fork is charged is composed of a hollow fork charging portion having a shape corresponding to an outer shape of the fork to be charged and a fork guiding portion formed continuous to one end side of the fork charging portion. The lid members are constructed to be independently swingable as well as movable backward and forward by lid member moving mechanisms, respectively.
When a fork is charged (inserted into the core tube), one of the lid members utilized when the fork is charged is swung towards the core tube so that the center of the lid member aligns with the axis of the core tube. The fork is positioned in the fork charging portion through the fork guiding portion through this operation. The lid member is then moved towards the core tube until the lid member abuts against the open end face of the core tube thereby closing the open end face thereof.
On the other hand, when the fork is uncharged, the other lid member utilized when the fork is uncharged is swung into position so that the center of the lid member aligns with the axis of the core tube. The lid member then advances towards the core tube until it abuts against the open end face of the core tube and thereby closes it.
In the conventional core tube opening and closing apparatus of the structure described above, the open end face of the core tube is closed by the lid member when the fork is charged. However, the lid member is provided with the fork charging portion and the fork guiding portion which is continuous to the fork charging portion and which is provided with an open end through which the fork passes. Accordingly, there is the fear that intruding cold air or dust may enter into the interior of the core tube through the open end of the fork guiding portion, i.e. the lid member, affecting the stable temperature distribution in the reactor core and adhering to the semiconductor wafer to lower the yield.